12 DECEMBER 2017
new, better stepper drivers and a more complex design (the four-layer PCB) increased the unit cost of the R17 stepper driver PCB
by about 20%. However, that increment was rapidly absorbed by
higher production volumes. Today the PCB’s unit cost is similar to the
previous version’s stepper driver PCB.
In addition, redesigning the stepper drivers allowed BCN3D to
release an upgrade kit. Because of the changes made in the stepper
driver ICs to achieve faster printer speed and accuracy, as well as
reduce noise and vibration, hundreds of users of the previous Sigma
model bought the new stepper drivers, creating a new income stream.
The small cost increment was therefore totally worth it.
BCN3D’s goal in approaching its prosumer market is to achieve a
balance of quality and price: price is important, but priority is given to
quality and functionality. Prices of 3D printers will continue to decline
not due to technological advancements, but with ongoing massification
of the technology. In general, although FFF 3D printers are not super
high-technology machines, they will get cheaper as more printer
manufacturers demand similar parts for their machine designs and
those part volumes increase, lowering part prices.
Pain Point #5 - The Increasing Importance
In keeping with BCN3D’s open source philosophy, the new stepper
driver modules have been designed to be mounted in any of its
Sigma printers, so users of the previous generation printer can benefit
from the R17’s improvements without having to modify the firmware.
Consequently, although the TMC driver IC has digital interface
capabilities, for this redesign BCN3D did not use them, so additional
time for firmware development and its testing were not required.
A good motion control design platform is affordable while also
powerful and capable of expansion. The ability to implement a motion
control solution in an existing product and know that its capabilities
can be expanded in future product generations with newer products
using the same design knowledge is very attractive/desirable.
In the future, motor control design will become even easier
and smarter. Offloading the main microcontroller from the motor
calculations is a must. This allows the use of S-shaped ramps on
multiple axes while keeping the MCU small. Also the S-shaped
speed curves reduce vibrations/jerk and optimize speeds. Finally,
technologies such as sensorless homing and sensorless, automatic
current adaption will improve motor efficiency and reduce system
Component/parts cost in volume
manufacturing: how much the component/
parts of the motion control functions will cost
when the end product is manufactured in
Total cost of ownership (TCO): TCO
can include development and non-recurring
engineering (NRE) costs, as well as system
costs, and the cost of enhancements,
replacements, and maintenance. A big
contributor to reducing TCO is reducing risk by
avoiding redesign cycles.
Development time: the complete amount
of time required to develop motion control
functions using a particular implementation
type (such as MCU, DSP, FPGA, off-the-shelf
ASSP, or OEM-owned ASIC) from conceptual
design to the end product being released to
Availability of components over the long
term: how long motion control components and
support for them will be available over the end
product’s lifetime before they become obsolete.
Performance and computational speed:
how well the motion control implementation
supports the end product’s requirements for
performance and computational speed. For
example, the main performance requirements for
3D printers are to be silent, accurate, efficient,
dynamic in behavior, and precise.
Real-time capability: how well the
motion control implementation supports the
end product’s requirements for real-time
performance. For example, in 3D printers
multiple axes need to be carefully controlled
in sync with each other for the most accurate
possible operation, especially when using two
Ease of printed-circuit board (PCB) layout:
how easy it is to lay out the PCB using a
particular implementation type, and taking into
consideration potentially constraining variables
such as heat dissipation and mechanical design.
Design platform flexibility: how easy it is to
adapt a design platform to other applications.
Reliability: how reliable the motion control
function and its components are over the end
Motor efficiency: how efficiently the motor
performs in terms of the end product’s
requirements, including energy savings/cost
savings, temperature, and regulatory restrictions.
Motion control quality: the quality of motor
control functions in the end product, such as
noise, smoothness, accuracy, and repeatability.
Figure 3. Block diagram of the
BCN3D R17 showing stepper
driver PCBs. Source: BCN3D